Spermexatin and spermexatol: new synthetic spermidine-based siderophore analogues

Syntheses of hexanediamine-based dihydroxamate (Hexamate), spermidine-based trihydroxamate (Spermexatins), and spermidine-based mixed siderophore analogues (Spermexatols) are described. Key intermediates include the N-hydroxysuccinimide esters of various hydroxamic acids, e.g., malonohydroxamate, succinohydroxamate, and glutarohydroxamate. These intermediates were synthesized, characterized, and incorporated as the ligating chains on spermidine. Also, mixed iron chelating compounds (Spermexatols) with both catechol and hydroxamic acid side chains were synthesized. The reagent carbobenzoxyimidazole was employed to distinguish between the primary and secondary amino groups of spermidine. The ability of these iron chelators to stimulate microbial growth is also described.